Sound absorbing structure



Feb. 16, 1960 GRUBER ETAL 2,924,857

SOUND ABSORBING STRUCTURE Filed Jan. 15, 1957 INVENTORS JOSEPH J. GRUBERy JOSEPH J.DeFALGO ll My? ATT NEYS United States Patent SOUND ABSORBINGSTRUCTURE Joseph J. Gruber, Depew, and Joseph J. De Falco, Buffalo,N.Y., assignors to Fenestra, Incorporated, Detroit, Mich., a corporationof Michigan Application January 15, 1957, Serial No. 634,273

Claims. (Cl. 204) The present invention relates to sound absorbingstructure.

It is an object of the present invention to provide sound absorbingstructure comprising a hollow building panel having one perforated wall,a sound absorbing member within said panel having a concave surface atthe side thereof adjacent said perforated wall, said surface beingtransversely concave for substantially the full Width of said member andextending for the full length thereof, said member having alongitudinally extending stifiening rib integrally formed therewith.

It is a further object of the present invention to provide soundabsorbing structure comprising a hollow building panel having aperforated front wall and a rear wall provided with a flange extendingtoward said perforated front wall, a sound absorbing member within saidpanel having its edge portions formed to extend toward the side thereofadjacent said perforated wall to space the surface of said member fromthe perforations in said wall, said member having a longitudinallyextending stiffening rib provided therein formed by compacting a centralzone of said member to provide a flange receiving groove at the rearthereof.

It is a further object of the present invention to provide soundabsorbing material for use with a metal ceiling, the material being of amolded construction having two outstanding legs along each lateral edgefor spacing the material away from the apertures in the panels, andhaving a groove along the length of the material intermediate theoutstanding legs to reinforce and strengthen the material.

It is a further object of the present invention to provide a soundabsorbing material in the form of a molded batt, for use with metalceiling panels, of a construction that is compact in form and not havingany loose materials on the surface to fall through the apertures in themetal panel with the material being compressed along the length of thebatt to form a reinforcing groove in the batt.

Other objects and features of the invention will become apparent as thedescription proceeds, especially when taken in conjunction with theaccompanying drawing illustrating a preferred embodiment of theinvention, wherein:

Figure 1 is a perspective view of a batt of the sound absorbingmaterial.

Figure 2 is a perspective view of the batt in place in a metal ceilingpanel.

Figure 3 is an end view slightly enlarged of the batt of sound absorbingmaterial.

Figure 4 is a fragmentary perspective view of a modified batt.

In the past sound absorbing walls and ceiiings have been produced byassembling together hollow building panels having the front or exposedwall thereof provided with a mutiplicity of relatively smallperforations. Sound absorbing material has been provided within thehollow interior of the panels to absorb the energy of sound en teringthe interior of the panels through the perforations.

In accordance with the present invention the sound absorbing'memberslocated within the hollow interior of the building panels are formed ofloosely aggregated fibers formed into a predetermined shape andcontaining suflicient binder material to render the members adequatelyform-sustaining.

Conveniently, the fibrous material may be glass fibers and the bindermaterial may be a suitable resin such for example as a phenolic resin.In producing the sound absorbing members or pads, they are fabricatedfrom a fleecy resilient superfine mass of glass fibers havingdistributed throughout a small quantity of the binder. The binder ispreferably a thermal setting resin and the pad is formed by a moldingprocess of thermally setting and curing the binder while the fibrous padis confined to the desired shape.

Referring now to the drawings, a batt of sound absorbing material isgenerally indicated at 10. The batt is in a molded form of generallyrectangular cross-sectional shape. Each lateral edge is rounded as at 12with the edge terminating in a continuous foot-like portion 14. Thesurface 16 extends upwardly and inwardly to join the bottom surface 18spaced from the top surfaces 20 and 22.

Intermediate the portions 14 the surface 20 is rounded as at 24 andextends downwardly and inwardly as at 26 to 2 8 and then parallel tosurface 18 as at 30 to 32. Surface 34 extends upwardly and outwardly towhere it is rounded at 36 to join surface 22.

The foregoing construction eliminates the necessity of providingseparate supporting means within the panel for supporting the fibroussound absorbing material in the proper position. In the past wire chairshave been required to support the padding material and to retain it inproperly spaced condition rearwardly of the perforated panel.

The batt can be fabricated from any suitable sound absorbing material,but glass fibre has excellent sound absorbing properties and whenlightly impregnated witha suitable binder such as a phenolic resin,readily molds to the desired form. The diameter of the fibers can varybut fibers having a diameter of .00011 of an inch have been found togive very satisfactory results.

In fabricating the batt the fibers are laid up in parallel layers sothat they have a horizontal orientation as indicated by the lines 40 inFigure 3. The uni-directional properties of the fibers give the battresiliency and strength to resist forces in a direction perpendicular tothe horizontal lay-up of the fibers.

The strength of the batt varies with the density of the fibers, thehigher the density of the fibers the stronger the batt. To increase thestrength of the batt the groove formed by surfaces 26, 30 and 34 isprovided. The groove is molded in the batt by compressing the fiberswith the density of the fibers increasing from the point 24 to 28 andreaching their maximum density along surface 30. The distance betweenthe surfaces 18 and 30 is approxi' mately one-third that of between 18and 20 with the fibers being approximately three times as dense between18 and 30 as those between 18 and 20. The increased density of thefibers along the groove increases the strength of the batt at thegroove. The molding process sets the fibers so that the groove retainsits form.

It will be understood that the shape and location of the groove and theamount the fibers are compressed can be varied to suit the strengthrequirements needed in the batt.

In Figure 2 the batt 10 is shown received in an acoustical treated metalceiling panel 50 which is comprised of a hat-shaped portion 52 which isattached to a flat plate 54 as by spot welding at 56 along the strips58. A plurality of apertures 60 perforate the plate and allow soundwaves to enter chamber 62 of the panel. To increase the strength of thepanel 50 the rib 64 is formed in the Patented Feb. 16, 1960 3 portion52. The batt is inserted through the open end into the chamber 62 withthe legs br'fe'et 14 resting on the inner surface of the plate 54.

It will be observed that the foot portion 14 spaces the surface 18 ofthe 'b'att away from the inner surface of the plate to prevent blockingbf the apertures 60 to allow sound waves to strike the batt and beabsorbed and the groove in the batt provides clearance for the rib 64.

In a typical example the finished pad may be produced from one pounddensity fiber glass pad originally about one and one-half inches thick,molded to approximately one inch thickand having its edge portionstapered to provide legs having an included angle of approximately 30degrees and provided to extend at'an inclination such that the surface16 makes an angle of approximately 30 degrees with a plane parallel tothe plane of the pad. The legs are located such that the fiat portion ofthe concave surface of the pad is spaced rearwardly approximatelyone-half inch from the plane containing the points of contacts of thelegs with the perforated plate 54. Since the batt from which the pad isproduced has an initial density of approximately one pound per cubicfoot, its compression to a thickness of one inch from an initialthickness of one and onehalf inches of course produces an averagedensity of approximately one and one-half pounds per cubic foot.Similarly, the compression of the intermediate zone to form thestiffening rib to a thickness of about one-third that of the padproduces a density in the stiffening rib of approximately four andone-half pounds per cubic foot. The stiffening rib 38 is approximatelyone inch wide. In compacting fibrous material of this type having atacky binder distributed throughout, the form-sustaining properties ofthe completed article-are increased very substantially by a small amountof compression or compacting. It has been found that the compacting ofthe fibers along the central zone of the pad to a thickness of somewhatless than half the thickness of the balance of the pad produces astrengthening and reinforcing effect much greater than would beexpected. The tapered edges are progressively degser toward the edge andat the extreme edge are quite sti In addition to the stiffness impartedby the strongly compressed and bonded together edge portions as well asthe intermediate stiffening rib 38 located between the surfaces 18 and30, it may in some cases be desirable to provide transversely extendingstiffening ribs which will interconnect the stiffened edge portions andthe longitudinally extending stiffening rib. In Figure 4 such a batt isindicated generally at 70. This batt is provided with the taperedforwardly or downwardly extending edge portions 72 providing theoutwardly or downwardly concave front surface indicated generally at 74,as well as the longitudinally extending intermediate compressedstiffening rib 76. In this case however, transversely extendingstiffening ribs indicated generally at 78 are provided formed bycompressing the material of the fibrous pad in transversely extendingelongated areas to a thickness of approximately one-third the thicknessof the uncompressed material. These transversely extending thickeningribs provide in effect a grid work of stiffening ribs which renders thewhole structure strongly self-support- It will of course be appreciatedthat if the sound ab- 'sorbing batts are required to be of a relativelygreater width than illustrated in the figures, two or more evenly spacedlongitudinally extending stiffening ribs may be provided.

The drawings and the foregoing specification constitute a description ofthe improved sound absorbing structure in such full, clear, concise andexact terms 'as to enable any person skilled in the art to practice theinvention, the scope of which is indicated by the appended claims.

What we claim as our inventionis:

1. Acoustical structure comprising an elongated hollow panel ofrectangular cross-section having one perforated -wall provided with amultiplicity of openings, an elonentire surface of said body adjacentsaid perforated wall 7 to be spaced therefrom, said body having astiffening rib extending longitudinally thereof formed of a zone inwhich said fibers are strongly compressed and bonded together intorelatively solid condition, the stiffening rib being formed by fiberscompressed from the side of said body opposite said concave side andforming a narrow groove thereat, said panel having a flange extendinginto its interior from the panel wall opposite said perforated wall andreceived in said groove.

2. A sound absorbing member for use in a hollow panel having aperforated lower wall, said member being a unitary one-piece elongatedbody composed in its entirety of loosely aggregated fibers lightlybonded together to render said body form-sustaining, the edge portionsof said body being compressed and shaped to extend downwardly from theintermediate portion of said body to form a longitudinally extendingdownwardly open channel, said compressed edge portions constitutingsupporting portions eflfective to support the intermediate body portionelevated above the perforated lower wall, a stiffening rib extendinglongitudinally of said body between its edge portions and in theintermediate elevated portion thereof, the fibers in said rib beingcompressed and bonded together to substantially higher density than inthe remainder of the intermediate portion of said body.

3. A sound absorbing member for use in a hollow panel having aperforated lower wall, said member being a unitary one-piece elongatedbody composed in its entirety of loosely aggregated fibers lightlybonded together to render said body form-sustaining, the edge portionsof said body being compressed and shaped to extend downwardly from theintermediate portion of said body to form a longitudinally extendingdownwardly open channel, said compressed edge portions constitutingsupporting portions effective to support the intermediate body portionelevated above the perforated lower wall, said body having alongitudinally extending inwardly depressed surface forming a grooveintermediate said edge portions and in the elevated intermediate portionthereof, the fibers inwardly of said depressed surface being compressedand bonded together to substantially higher density than in theremainder of the intermediate portion of said body to form a stiffeningrib.

4. A member as defined in claim 3 in which said groove is formeddownwardly in the top surface of said body.

5. A member as defined in claim 3 in which the portion of said soundabsorbing member outside of said stiffening rib has a density of aboutone and one-half pounds per cubic foot and in which the compressedmaterial of the stiffening rib has a maximum density of approximatelyfour and'one-half pounds per cubic foot.

References Cited in the file of this patent UNITED STATES PATENTS1,825,770 Barnett y Oct. 6, 1931 1,874,659 Upson Aug. 30, 1932 1,957,822Denning May 8, 1934 2,073,036 Voight e Mar. 9, 1937 2,077,889 Mazer Apr.20,1937 2,187,335 Wagner Jan. 16, 1940 2,357,560 Taforo Sept. 5, 19442,450,911 Parket al. Oct. 12, 1948 2,576,698 vRussum Nov. 27, 1951

